drm/i915/dp_mst: Fix forced link retrain handling in MST HPD IRQ handler

Handling of a forced link retraining debugfs request via the DP MST HPD
IRQ handler is incorrectly skipped, if the IRQ handler doesn't see any
HPD IRQs raised by the sink. Fix this by ensuring that the request is
always handled (in the Fixes: commit below by directly calling
intel_dp_check_link_state(), later by the same call moved to
intel_dp_handle_link_service_irq()).

Cc: Luca Coelho <luciano.coelho@intel.com>
Fixes: db4855d90363 ("drm/i915/dp_mst: Reuse intel_dp_check_link_state() in the HPD IRQ handler")
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20260311153152.133744-1-imre.deak@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index fbb5e2f9c2414123bec81cdba2ed76339c4af262..2ae030eda73ee4aeb7d2cd7b6627379ea8947258 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -5575,11 +5575,13 @@ static bool
 intel_dp_check_mst_status(struct intel_dp *intel_dp)
 {
        struct intel_display *display = to_intel_display(intel_dp);
+       bool force_retrain = intel_dp->link.force_retrain;
        bool reprobe_needed = false;
 
        for (;;) {
                u8 esi[4] = {};
                u8 ack[4] = {};
+               bool new_irqs;
 
                if (!intel_dp_get_sink_irq_esi(intel_dp, esi)) {
                        drm_dbg_kms(display->drm,
@@ -5595,20 +5597,28 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
 
                intel_dp_mst_hpd_irq(intel_dp, esi, ack);
 
-               if (mem_is_zero(ack, sizeof(ack)))
-                       break;
+               new_irqs = !mem_is_zero(ack, sizeof(ack));
 
                drm_WARN_ON(display->drm, ack[1] & ~INTEL_DP_DEVICE_SERVICE_IRQ_MASK_MST);
                drm_WARN_ON(display->drm, ack[3] & ~INTEL_DP_LINK_SERVICE_IRQ_MASK_MST);
 
-               if (!intel_dp_ack_sink_irq_esi(intel_dp, ack))
+               if (new_irqs && !intel_dp_ack_sink_irq_esi(intel_dp, ack))
                        drm_dbg_kms(display->drm, "Failed to ack ESI\n");
 
                if (ack[1] & (DP_DOWN_REP_MSG_RDY | DP_UP_REQ_MSG_RDY))
                        drm_dp_mst_hpd_irq_send_new_request(&intel_dp->mst.mgr);
 
+               if (force_retrain) {
+                       /* Defer forced retraining to the regular link status check. */
+                       ack[3] |= LINK_STATUS_CHANGED;
+                       force_retrain = false;
+               }
+
                if (intel_dp_handle_link_service_irq(intel_dp, ack[3]))
                        reprobe_needed = true;
+
+               if (!new_irqs)
+                       break;
        }
 
        return !reprobe_needed;